Mono Upgrade the .NET upgrade version constantly crashes

Running the Feb 2 version on Win7 64-bit - I get random (but constant, I'd say 20% of the time I do something like recompile or launch) crashes. The editor plain disappears without a trace.
The log always ends like so (2 examples)
Packing sprites:
- Repacking is not required. Check took 21.358618 ms.
Reloading assemblies for play mode.
Begin MonoManager ReloadAssembly

WeaveAssemblies unityPath= C:/Program Files/Unity/Editor/Data/Managed/UnityEngine.dll
WeaveAssemblies unetPath= C:/Program Files/Unity/Editor/Data/UnityExtensions/Unity/Networking/UnityEngine.Networking.dll
Reloading assemblies after finishing script compilation.
Begin MonoManager ReloadAssembly

Anything else useful I can provide for this?

 

The log doesn't contain the callstack... the editor just disappears without so much as a puff of smoke The log file similarly just terminates after the Begin... line
That doesn't happen with 5.4.2f2 that I'm currently using. The only code I was using that is not in .NET 2.0 was System.IO.Pipes.

Just tried again, I can repro fairly easily.
However, I just found that the code I needed (named pipes) is actually available in Unity with "full .NET 2.0", so I gave up on the new client. Sorry Until it can support native libraries, what I'm trying to use is Google.OrTools, thru the named pipes based wrapper.
Anyway.

In the event log, there's a crash of VS StandardCollector that SEEMS to be associated with the failure; it happens a few minutes later as follows.
Faulting application name: StandardCollector.Service.exe, version: 14.0.25123.0, time stamp: 0x56f2261c
Faulting module name: ntdll.dll, version: 6.1.7601.23572, time stamp: 0x57fd0651
Exception code: 0xc000000d
Fault offset: 0x00000000000689f2
Faulting process id: 0x1c60
Faulting application start time: 0x01d296311e2ab25f
Faulting application path: C:\Program Files (x86)\Microsoft Visual Studio 14.0\Team Tools\DiagnosticsHub\Collector\StandardCollector.Service.exe
Faulting module path: C:\Windows\SYSTEM32\ntdll.dll
Report Id: 19d6b5ab-0225-11e7-9539-6cf049518216

There are no errors at the time of the Unity issue itself.
Although this time I failed to save the log, the issue happened the same way. I can attach a previous log, however the forum now tells me .log is not an allowed extension.
As a side note it would help if logs had timestamps in them and weren't deleted after 2 restarts

This looks like something machine-specific to me, but if you are interested in trying, the project is on github (it's a playground so it's not in a good state...), I upgraded with this commit (no pipes usage yet, if it matters) - https://github.com/sershe84/hexgrid/tree/e3cf32d22cf5712a4133e298cf1e3cafb934c44d
and this is the last state before downgrade... https://github.com/sershe84/hexgrid/tree/9116d978a8e560174b7aa89ded634c46757b9708
On my machine you don't need to do much, just modify code in VS/rebuild/start/stop a few times (I have auto-rebuild disabled, if it matters), and eventually the editor will disappear.